System for locating radiated-signal reflectors



Patented Sept. 3, 1946 t 1 UNITED STATES PATENT FFICE SYSTEM, FOR noca'rmo were- SIGNAL narnscrons Arthur V. Loughren, Great Neck, N. 'Y., assignor, by mesne assignments, to Hazeltine Research, Inc., Chicago, 111., a corporation of Illinois Application May 26, 1941, Serial No. 395,172

9 Claims.

This invention relates to radiated-signal reflectcr locating systems and, particularly, to such systems of the type in which a predetemiined space is scanned with a sharply-concentrated.

radiated beam in order to locate a radiated-sigrial deflector, such asan aircraft.

It has been proposed in aircraft locating systems to scan a predetermined space in two directions with a sharply-concentrated radiated beam of wave signals and to receive thesignal whichis reflected from the aircraft to provide an indication of its direction from the locating station. It has also been proposed to deflect the radiated beam at a different frequency in each of two directions in order to scan a. given space and to utilize a cathode-ray tube at the receiving station as the direction-indicating device,

the electron beam of the cathode-ray tube being deflected synchronously with the deflection of the radiated beam. However, such systems of the 20 prior arthave had the disadvantage that mechanical beam-deflecting arrangements were necessary for causing the radiated beam to scan the desired space. The general disadvantages of mechanical scanning. arrangements are well understood by those skilled in the television art and manyof these disadvantages are also present in mechanical scanning arrangements of the type under consideration.

.It is an object of the present invention, therefore, to provide an improved system for determining the direction from a locating station of a radiated-signal reflector, such as an aircraft It is still another object of the invention to provide an improved system for determining the direction of, and the distance to, a radiatedsignal reflector, such as an aircraft, from a locating station.

In accordance with a feature of the invention,

a system forlocating a radiated-signal reflector comprises a radiating system having-a radiation characteristic'efiectively in the form of a sharply concentrated beam, means for applying a carrier signal to the radiating system, and means for varying the frequency of the carrier signal to 45 scan a predetermined space in at least one direction with the beam. The system also includes means for receiving energy from the radiated beam reflected from the reflector and for utilizing the received energy to indicate the direction of the reflector, and means responsive jointly to the aforesaid frequency-modulated signal and the reflected signal for determining the distance of the radiated-signal reflector from the locating system.

Also in accordance with a feature of the invention, the last-mentioned system may include a reproducing device including an indicating area corresponding to the predetermined space 5 scanned by the radiated beam, means responsive to the received energy for producing an indicationthereof of restricted area on the indicating area, and means for scanning the reproducing device in synchronism with the radiated scannin beam. By this arrangement, the position of the indication on the indicating area is dependent upon the direction of said radiated-signal reflector. I

Also in accordance with a feature of the invention, a system for locating a radiated-signal reflector comprises, a radiating system having a radiation characteristic effectively in the form of a sharply-concentrated beam, means for applying a carrier signal to said radiating system, and means for scanning a predetermined space with the beam. This system also comprises means for receiving energy from the radiated beam reflected from the reflector and for utilizing the received energy to indicate the approximate direction of the reflector, and means for compensating the indication for the time required for the received energy to travel from said radiating "system to .said means for receiving the radiated beam reflected from the reflector.

For a better understanding of theinvention,

together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

Fig. 1, of the drawings is a circuit diagram, partly schematic, of a system for scanning a predetermined space with a sharply-concentrated radiated beam of wave signals; Fig. 1a comprises a set of graphs which are used in explaining a .portion of the operation of the arrangement of Fig. 1; Fig. 2 is a circuit diagram, partly schematic, of a system embodying the beam-radiating system of Fig. 1 for locating a radiated-signal reflector, such as an aircraft; while Fig. 3 is a circuit diagram, partly schematic, of a modification of the radiated-signal reflector locating .system of Fig.2.

Refen'ingnow more particularly to Fig. 1 of the drawings, the system there represented is disclosed and claimed in a divisional application Serial No. 418,712, filed Nov. 12, 1941. The system comprises an antenna or radiating system l0, means for applying a wave signal'to the antenna system for directive, radiation effectively in the form of a sharply-concentrated beam, and means for cylically varying the frequency of the wave signal and, by virtue of the antenna chartal arrays and are arranged, in the order named,

to one side of the set of dipoles D1-Da, inclusive,

ing an array of six dipole antennae and the sets being spaced in a'second dimension. The dipoles of each of the above-mentioned sets of dipoles are energized in parallel except that the abovementioned electrical spacing in the one dimension between the individual dipoles of the sets is provided by delay networks F interposed between adjacent dipoles. Th geometrical spacing of the dipoles in each set in the above-mentioned one dimension is preferably made ap-' proximately one-half wave length of the mean or nominal frequency of the wave signal to be applied to the system, while the electrical spacing due to delay networks F, F is made to be an integral number of wave lengths at the nominal or mean frequency of the system. The sets of dipoles are also preferably spaced in the dimension normal to the sets, or in' the above-mentioned second dimension, by a, distance approximately equal to one-half the wave length of the mean or nominal frequency of the wave signal -to be applied to the system.

The means for applying a wave signal to the antenna system In for directive radiation effectively in the form of a sharply-concentrated beam comprises a high-frequency oscillator ll of any suitable type adapted for frequency modulation individually coupled to each of the sets of dipoles through transformers Ta, Tb, To, and Ta having their primary windings connected in series and coupled to. the high-frequency oscillator II and their respective secondary windings coupled to the above-mentioned sets of dipoles through phase shifters (2 a, l2b, I20, and [2d, respectively, which have the same phase shift at the nominal or mean value of the field-frequency generator.

In order to vary the relative phase of the signals as applied to the signal radiators of antenna system In which are spaced in the above-mentioned one dimension at a Ufirst predetermined frequency, there is provided means for varying in a predetermined cyclic manner the frequency of The antenna system H] includes a pludimension at a second predetermined frequency. there is provided a field-frequency generator 15, also adapted to be synchronized by timer [4 and having an output circuit coupled across a voltagedivider resistor 9, the mid-tapof which is grounded. A control voltage is derived from one end of resistor 9 and utilized to control phase shifter While a voltage of opposite polarity is derived from the other end of resistor 9 and utilized to control phase shifter l2d. Control voltages for phase shifters lZb and I20 are derived from intermediate points on resistor 9 as illustrated in the drawings. The phase shifters I'm-12d, inclusive, may be of any conventional type and it is to be understood that the phase shift of each of these units is dependent upon the magnitude and polarity of the control voltage to form an array of dipole sets, each set includderived from the resistor 9 for the particular unit under consideration.

In order to suppress radiation downward from the plane including the conductors of dipoles Dl-D24, inclusive, a reflecting conductor [1 is disposed below each of the dipoles. Thes reflectors increase the useful energy in the desired direction of radiation and minimize minor spurious beams.

In considering the operation of the system of Fig. l and neglecting for the moment the functions of generators l3 and IE, it will be seen that the system comprises a plurality of directional signal radiators geometrically spaced in the above-mentioned first dimension and in the above-mentioned second dimension and that the signal radiators which are geometrically spaced in the first dimension are also electrically spaced by a time-phase displacement due to time-delay units F. Considering for the moment only the the signal developed by the high-frequency oscillator II atthe above-mentioned first prede-' ,termined frequency. Specifically, there i proset .of dipoles Dl-DB, inclusive, in the condition where they are all excited in the same phase, it is seen that this is a known form of antenna array by which the radiation is concentrated relative to the radiation pattern of a single dipole. The concentration of energy into the beam takes place at the expense of the regions generally in the direction of the ends of the row of dipoles. Furthermore, it is seen that the reflectors I 1 limit or suppress a substantial part of the radiation in the direction in which they are spaced from their associated dipole conductors. The resulting radiation pattern has a fan-shaped configuration with its major dimension vertically above the row of dipoles, its smallest dimension parallel to the row,.and its intermediat dimension parallel to the individual dipoles.

I The effect of adding the other sets of dipoles is to concentrate the radiated signal to the form of a sharply-concentrated beam. In the case where all rows are excited with a common phase the direction of this beamwill be at right angles to the plane of the complete array. The reason for thi is that the signals radiated from any pair of cyclically and directly in accordance with its developed by linefrequency generator IS, in any conventional manner.

In order to vary the relative phase of the signals as applied to the signal radiators of antenna In which are spaced in the above-mentioned second wave form, which is preferably a linear saw-tooth wave form. Due to the fact that the dipoles of each of the above-mentioned sets are electrically spaced by the time-delay networks F, the effect of this frequency variation is to vary the relative phase of the excitation of the dipoles of each set. Thus, for a frequency somewhat different than the nominal or mean frequency of the systhis generator.

' tern, the signals radiated by each of a pair of adjacent dipoles of a set are not in phase in the vertical direction but are in phase in a direc- If the effect of field-frequency generator I5 is now considered, it is seen that the voltageoutscanned by the beam which is radiated from. afiput of this generator, which is also preferably of v a linear saw-tooth wave form, is effective to vary the relative phase of the dipoleswhich are spaced in the above-mentioned second dimension at the frequency of this generator. Reference is made to Fig. In for an-explanation of the operation of Thus, curves I 1a, "b, He, and ||d represent the control voltages applied to phase shifters |2a, i2b, He, and l2d, respectively. It is thus seen that. at the beginning of the fieldtrace period, the signals applied to sets of dipoles D1-Da, inclusive, and Dr-Du, inclusive are shifted in phase in onesense and by different amounts and that the signals applied to sets of dipoles D13Dll, inclusive, and Die-D24, inclusive, are correspondingly shifted in phase in the opposite sense and by different amounts. The result of this excitation is to tilt the transmitted beam in the above-mentioned second dimension because it is only in such a direction that the signals radiated by two adjacent dipoles which are spaced in the second dimension, for example, dipoles Da and Du, are exactly in phase. Furthermore, it is seen that the amount of this tilt in the second dimension changes during the field-scanning period due to the change of relative excitation phase of the sets of dipoles effected by field-scanning generator i5. Specifically, the amount of tilt in the second dimension decreases tozero, at which time the beam is vertical and then increases in the opposite sense. The arrangement of Fig. 1 is thus effective to vary the direction of transmission of the sharply-concentrated beam in two directions to scan a predetermined space with the beam.

The system of Fig. 2 is one for locating a radiated-signal reflector, such as an airplane 2|), and comprises a system for scanning a predetermined space, including the airplane with a sharply-concentratedbeam, such as .was described in detail in connection with Fig.1. Circult elements of Fig. 2 which correspond to those of Fig. 1 have identical reference numerals.- In addition to the elements of the system of Fig. 1, the locating system of Fig. 2 comprises means for receiving energy from the beam radiated by the antenna system l0 and reflected from the radiated signal reflector 20. This means comprises a wave-signal receiver 2| having a substantially nondirectional antenna system provided by two dipole antennae 22, 23, antenna 22 preferably being parallel to the dipoles of antenna l0 and antenna "being at right anglesthereto to provide a response to reflected waves having the polarization withwhich they were originally radiated or a polarizationQO degrees displaced from that radiated by antenna Ill. The system includes a signal-reproducing device having an indicating area corresponding to, the predetermined space tenna system It. This reproducing device comprises cathode-ray tube 24 of a conventional type having a fluorescent screen 25 which is the indicating area. The signal output of receiver 2| is applied to the input circuit of cathode-ray tube 24 to provide an indication of a received signal of restricted area on the indicating area 25. Cathode-ray tube 24 is so biased by a source l9 that it is cut off in the absence of a received signal. Suitable operating potentials are provided for cathode-ray tube 24 in a manner well understood in the art. There are also provided means for scanning the reproducing device 24 in synchronism with the radiated scanning beam from antenna system I0 sothat the position of an indicating spot on fluorescent screen 25 is dependent upon the direction of the plane 20 from the antenna system l0. The scanning means comprises line-scanning plates 26, 21 and field-scanning plates 2&29 towhich are applied, respectively, scann I voltages of the wave forms and frequencies of the signals generated by generators l3 and I5, respectively. the line-scanning volt- :ge being applied to plate 21 through a resistor The system of Fig. 2 also includes means responsive to the frequency variation of oscillator II for utilizing the received energy which is reflected'from airplane 20 for selectively determining the distance of the airplane 20 from the locating system. This means comprises a heterodyne modulator "to one input circuit of which'is applied a signal output of high-frequency generator through a limiter 34 and to another input circult of which is applied a signal output from receiver 2| through a limiter 38. The arrangement for indicating distance also comprises, coupled in cascade to the output circuit of modulator 32, a frequency-responsive network and detector 35, responsive to beat notes representing the difference frequency of the signal inputs to modulator 32 and preferably having a linear characteristlc over the range of beat-note frequencies encountered in operation, and a distance indicator 38.

Due to the fact that more than one airplane may be in the space scanned by'the beam from antenna system In at the same time, several indications, as indicated by. the dots on fluorescent screen 25, may be produced simultaneously and the distance indicator 38 will, in general, indicate a distance for each of these airplanes. In order to provide means to facilitate the determination of which of the positions indicated on fluorescent screen 25 corresponds to a particular distance indication of distance indicator 2!, the

unit 38 is provided. The unit 38 comprises an unlocking device for distance indicator 38 such that, inthe absence of a signal input to the unlockingdevice, a distance indication is not developed by indicator 36. In order to energize the unit 38 in accordance with any desired received direction indication on fluorescent screen 25, there is provided a photocell 40, around which there is a shield 4| having a relatively narrow aperture 42. The output circuit of photocell 40 is connected in cascade through an amplifier 43 v which may be sufficient to give an inaccurate indication in the line-scanning direction al- Therefore, in order to compensate, the direction indication on fluorescent screen 25 for this time delay, an output circuit of detector is. coupled across resistor 30. I

Coming 'now to" the operationjofthe locating system of Fig.2, it will first be assumed that distance indicator 36 is not locked so that it is continuously in a condition for operation and temporarily the functions of the unlocking device 38 and the scanning compensating circuit including resistor 30 will be neglected. The operation of the beam-scanning arrangement including antenna system 10 being exactly the same as that described in connection with the description of the operation of Fig. -1,.a further description thereof is unnecessary herein. [In considering the operation of -the remainder of the system of Fig- 2 under the conditionsassumed, it will be seen that the cathode-ray beam of tube 24 is caused toscanthe. fluorescent screen 25 synchronously with the scanning of the predeterminedsky space by the beam'radiated from antenna system l. Sinc tube 24 is normally biased beyond its cutoff point but is operated above its cutofl point for received signals from receiver 2i, a spot indication .is provided on the fluorescent screen 25 for each airplane in the field scanned. Also, since the signal received by receiver- 2| is delayed in time with reference to the signal output of. high-frequency oscillator I l by the time interval. required for the signal to travel from antenna [6 out to airplane 20 and bach'to the-antenna 23', and since the frequency of oscillator li has been altered during this time by the action i line-frequency generator l3, the

difference frequency. ofthese two signals is a varies at a uniform; rate with time and, there forepany predetermined beat-frequency component derived from modulator 32 represents the same time delay-or distance regardless of the direction in which the signal from antenna I0 was radiated. v

Every airplane in the field scanned by the beam radiated from antenna 10, therefore, is effective to provide a direction indicationon fluorescent screen 25 and a distance indication on distance indicator 36.

-ing which direction indication correspondswith a particular distance indication that the unit 38 is provided. Thus, in-considering the operation oi'this portion of the system, it will be seen that, by moving aperture 42 across fluorescentscreen 25, radiated energy from any of the direction-indicating spots on fluorescent screen 25 maybe caused to energize photoelectric cell 40. The signal output of the cell is amplified in amplifier 43, differentiatedin diiferentiating circuit 44, and utilized to overcome the normal cutoff bias on distance indicator 36 so that it develops a dis- It is for the purpose of determin- 8- tance indication only for toelectric cell 46. The diiferentiating circuit 44 is provided so that the distance indicator is responsive only to relatively rapid changes in the signal input to photocell 40. Such a rapid developed each time the scanning beam of tube .24 becomes incident upon the particular spot on r the fluorescent screen 25 which is being utilized to supply energy to photocell 46. The fluorescent material on the end of tube 24 will, in general, have'a considerable time of luminescent decay which is disregarded by the differentiating circuit 44.;

' Coming now to the arrangement of Fig.2 for compensating the direction indications on fluorescent screen'25 for the time required for'the radiated beam totravelfrom antenna ill to the airplane 20 and backtoantenna system 22, 23, it will be seen that each time the signal input to tube 24 causes the tube to be operated above its cutoff point, the signal output from frequency detector 35 is also effective on the s'canningplates 26, 21 oitube 24. The circuit is so adjusted that.

the amplitude and polarity of this signal output is effective momentarily to "back up or retard the line-scanning potential of tube 24to cause it to correspond with the corresponding line-scanning potential of generator l3 at the time the signal being received left the antenna l0.- The compensating arrangement including resistor 30 may be subject to an error. for airplane 'which are near the line-scanning boundaries of fluorescent screen.25. However, in practice, the antenna system It! can be mounted upon a movable platform.

so that, in general, the indication for any airplane can be brought well within the indicating area 25. On the other hand, to prevent false indications of the type just mentioned, a mask can be disposed around the fluorescent screen 25 to mask the indication of any plane which may give such a false reading.

The arrangement of Fig.3 illustrates 'a modiflcation of the system of Fig. 2 forindicating the component of direction corresponding to one of the scanning dimensions of antenna system ID for all received signals. All of the portions of Fig. 2 maybe included in the system of Fig. 3,

although forsimplicity some of the portions of Fig. 2 are not included, and elements which are similar in the preceding figures have identical reference numerals. The system of Fig. 3 comprises a cathode-ray tube-56 of conventional de-' sign having a fluorescent screen 5| and having its input circuit coupled to the wave-signal receiver 2| in the same manner as was described abovein connection with the cathode-ray tube 24 of Fig; 2. .However, one'set of scanning plates 54, 55 of cathode-ray tube 50 is-coupled' directly across anoutput circuit of detector 35, while the other set of scanning plates 52, 53 is connected between the movable blade of a single-pole,

" double-throw switch 56 and ground. Line-scanscanning generator I3.

ning generator I3 is connected to one contact 51 of switch 56 through a'resistor 3ll,'the function of which is similar to that of resistor 30 of Fig. 2, andfield-scanning generator I5 is connected to the other contact 58.

In consideringthe operation of the'circuit of,

Fig. 3, it willfirstbe assumed that the blade of switch. 56 is operated to its upper contact 51 so that scanning plates 52,53 are energized by line The operation of elements, the reference numerals of which correthe particular signal which is, at the moment supplying. energy'to phoray beam is deflected in one direction in accord ance with the distance of the airplane from which the reflected energy is received and is deflected in the other direction in synchronism with the line scanning of the radiated beam. Therefore, a trace is developed on fluorescent screen consisting of a narrow upswing representing the airplane. -The amplitude of such upswing, which may be measured from a horizontal indicating line on the end of the tube,'represents the distance of the airplane, and its position laterally across the screen represents the corresponding line-scanning co-ordinate. Similarly, the blade of switch 56 may be closed in its lower contact 58 and the corresponding field-scanning coordinate may be obtained. Thus, the modification of the invention illustrated in Fig. 3 is efiective to providean indication both of direction and of distance for any airplane in the field scanned by the beam from antenna I0. If two airplanes are present at a given time in this field, indications will be received for each airplane. However, in

general, these airplanes will not be at the same distance and, for this reason, the line-scanning and field-scanning co.-ordinates corresponding to each airplane can be readily determined. It will be fully understood that the indicator tube 50 of Fig. 3 can be used in conjunction with the indicator tube 24 of Fig. 2, and it will be seen that the indications provided by screens 25 and 5| together are analogous to the three projections of a set of points in space.

While applicant does not intend to limit the.

invention to any particular design constants, the

following value are appropriate for an airplanelocating system:

Mean or normal frequency .for oscillator 11 100-1000 megacycles While a nondirectional antenna has been illustrated in connection with receiver 2 I, it will be appreciated that there are particular advantages to be gained in utilizing an antenna structure for the receiver which is similar to antenna I 0. If such an antenna is used it has the property of beinghighly directional for only the signals received due to reflection as described above. The reason for this is that its directive proper- While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modiflcations may be made therein without departing from the invention. and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A system for locating a radiated-signal reflector comprising, a radiating system having a radiation characteristic effectively in the form of a sharply-concentrated beam, means for applying a carrier signal to said radiating system,

means for'varyingthefrequency of said carrier signal to scan a predetermined space in at least one direction with said beam, means for receiving energy from said radiated beam reflected from said reflector and for utilizing said received energy to indicate the direction of said reflector, and means responsive jointly to said frequencymodulated signal and said reflected signal for determining the distance of said radiated-signal reflector from said locating system.

2. A system for locating a radiated-signal reflector comprising, a radiating system having a radiation characteristic efi'ectively in the form of a sharply-concentrated beam, means for applying a carrier signal to said radiating system, means for varying the frequency of said carrier signal to scan a predetermined space in one direction with said beam, means for receiving energy from said radiated beam reflected from said reflector and for utilizing said received energy to indicate th direction of said reflector, means for heterodyning the transmitted signal and said received reflected signal to derive beat notes dependent upon the frequency difierence therebetween, anda requency detector responsive to said beat notes for indicating the distance of said radiated-signal reflector from said locating 7 system.

3. A system for locating a radiated-signal reflector comprisirfg, a' radiating system having a radiation characteristic efiectively in the form of a sharply-concentrated beam, means for applyinga carrier signal to said radiating system, means for scanning a predetermined space with said beam, means for receiving energy from said radiated beam reflected from said reflector and for utilizing sa'id received energy to indicate the approximate direction of said reflector, and

1 means for compensating said indication for the ties vary with frequency in a manner analogous to that described above in connection with the description ofthe operation of antenna 10. If

an antenna similar to that of antenna I0 is used at the receiver, it is necessary to provide phase shifters corresponding to I2a-l2d, inclusive, of

Fig. 1, the corresponding phase shifters at the receiver being controlled in exactly the same manner that those at the transmitter are controlled. In such a receiving system, the receiver proper is analogous to high-frequency oscillator ing system.

time required for said received energy to travel from said radiating system to said means for re ceiving the radiated beam reflected from said reflector. w

4. A system for locating a radiated-signal reflector comprising, a radiating system having a radiation characteristic effectively in the form of a sharply-concentrated beam, means for applying a carrier signal to said radiating system. means for scanning a predetermined space with said-beam, means for receiving energy from said radiatedv beam reflected from said reflector, a reproducing device including an indicating area corresponding to said predetermined space, means responsive to said received energy for producing an indication thereof of restricted area on said indicating area, means for scanning said reproducing device in synchronism with radiating: system and said-means for receiving energy from said radiated beamjwhere; by, the o'sition of said indicationon" said i dicating area ii's' depe dent upon "the direction 01 saidrefiector., 5. a mior ating'fa radiatedfsignal re b teb pr ne a edi iiie i mthi i 1 plurality of Z s'ignal radiators 'g em triw11y s acea in two dimensions, a sourc'efof wa ignals means o ei d a lyv l ln e ,sne s'iir m source to saidfsignal radiators tor directive radiation effectively jin'the' iforrn hi '8. sharply concentrated' beam; mea sror 'eflectivelyf varying the i v "1 1 tween said 7 e a v h' is o emi 1 mb w rmed 'a d hich are spaced in one of said signal radiators w dimensions fat I S o 5 nals eaapp ie spaced inthe othe e rlative'f'phas'e of-said- {si signal radiators which are rne'nsion at a second prer i ed-frequency;merepyto' vary the direeaonb'rj tr'a'ris'missionpf "said radiated beamtwo dimensions tq sc'an'ap edetermineds ace, 'means for receiving energy ti-om said radiatedMani reflec't'ed 'from said' -reflectoni a'-reproducing"device including an n'dicatirig area correspondi'ng 1 to st predetermined irequenc y;

cyclic manner'ieflectively-to vary the relative'phase or the si'gfnals as applied to said raldia'tors'which are spaced msampne dimension at a'flrst predetermined'frequency,-means for varying the relative phase of said'signal as a'ppliedto said signal radiators which' are spaced in the other dimensi'cln ata second predetermined frequency thereby to lv'a'ry-"the direction' of transmission of said radiated in two dimensions to scan ai-predetermin'ed' space: means for receiving 'energyafro'm 'said'radiated beam reflected iroms'aid refiector;- 'a

reproducing device including anindicating area corresponding to said predetermined space, means responsive to: said received energy for producing anindication thereof of a=restricted area onsaid indicating area; means ior scanning' said reproducing'devicein synchronism with said 'radiated 'scanning -beam; -whereby 'the'position of said. indicationon said-indicating area is dependent upon th posltion or said reflectonand means. dependent upon'thefrequencyvariation of said carrier "signal 'and'responsive tozthe frequency of said "received energy tor -indicating 1 the distance of saidf'predetermined; spacermeans'wesponsive to and means fonscanningsaid reproducing device insynchro'nism' with'saidiadiated scanning beam,-, whereby t'he 'p ien 'of, said' indic'ation' on -s i inuicating area 6. A system forlocatinga pluralityofjradiatedsignal "reflectors comprising; a-raidiating system? having a radiation characteristic effectively in the f orni of- 'a' sharply-concentratedbeam; means for applying a c'arrier -signalto "fs'ai'd radiatin system; means for varying-the frequency ot-"sa;id carrier signal to =scan a predetermined space in one direction with said'beam, means for: receiving energy froin said radiated beam reflected from said reflectors and 'for utilizing said receivedenergy to indicates the directions'oi' saidreflectors.

and means for selectively indicating :the distance i of any of said signal": reflectors fromithe locating systemp v,; 1 Yr 7. Aisy'ste'm for locating azradiated-signal reflector comprising, -a=radiating system including a plurality of signal radiators geometrically spaced.

in two dimensions :means 'for electrically spacing :them in one of the two dimensions; a source of high-frequency wave signals, means for individually applying wave. signalsirom said source'to' said signal radiators 'ior directive" radiv ation eiiectively.inthe form of a sharply-concentrated beamymeans comprising'said' electrical spacing means and means for varying the frequency of said-wave signals in a predetermined j said received energy for producing an indication I thereof of restricted'area'on saidindicatirigarea,

1 said reflector from" said *locating system; i ll 8; Aysystem for loca'ting'a' plurality of radiated signal reflectors comprising, a radiating system havingaradiationcharacteristic efiectively in the J w-formoot a'sharply-concentrated beam; means for applying a carrier signal to saidradiating system, means for varying; the frequency of said carrier signal'toscan a predetermined-space in one direction: with said beam,"v means for. receiving energy wiromis'aid radiatedubeam reflected from said re- ;v-flectors and for: utilizing received energy to indicats witheldistance" and the component ,of direction corresponding to said scanning direction for s all of said signal reflectors; r

9. A system for locating a'pluralityoi radi- .;a,tedi-signal reflectors comprising-a radiating systern having a radiationcharacteristiceffectively in the form-3 of 3a sharplygconcentrated beam, means for applying a carrier signal'tosaid radiating system, means for varying. the frequency of said carrier, signal to scan a"predetermined'space in one direction with said beam, a cathode-ray signal reproducing tube,'meansfor receiving energy'from'said radiated beam reflected from said reflectors and for, utilizing" received energy to control the beam ,of said'tube, means for deriving from said received signalsand said frequency-modulated carrier signal a signal indicative of distance'f'or each of said signal reflectors,. means for deflecting the cathode-ray beam of said tube in one. direction ,in accordance with said last-mentioned signals, and means for deflecting the cathode-ray beam of said tube in another direction in synchronism, withsaid scanning of said radiated beam. a H ARTHUR V. LOUGHREN. 

